Nansen bottle,ocean-water sampler devised late in the 19th century by the Norwegian oceanographer Fridtjof Nansen and subsequently modified by various workers. The standard Nansen bottle is made of metal and has a capacity of 1.25 litresand . It is equipped with plug valves at either end. The bottle is affixed to a winch wire with its valves open, and the winch wire is paid out until the bottle is approximately at its desired sampling depth. A weight, or “messenger,” is then allowed to slide down the cable. The upper attachment of the Nansen bottle is disengaged from the cable by the impact of the messenger; and the bottle is reversed end over end, its valves closing in the process to trap the water sample. Thermometers usually are attached to the Nansen bottle to record the temperature and pressure of the sample site. Several Nansen bottles are employed during a single hydrographic cast, each bottle releasing another messenger when tripped, in order to trigger the deeper bottles in turn.

The Niskin bottle, created by American inventor Shale Niskin in 1966, is more widely used than the Nansen bottle in modern ocean-water sampling activities. Although it is similar to the Nansen bottle in most respects, the Niskin bottle is viewed as an improvement over Nansen’s design because of its plastic construction and because it does not require end-over-end movement to collect samples.